Patent GB-1018225-A (GB)
Title: Methods and apparatus for welding seams employing high frequency electrical currents
IPC: B23K13/02
Filed: 1962-10-11
Abstract: 1,018,225. Making longitudinally seamed tubes; welding by pressure; bending. AMERICAN MACHINE & FOUNDRY CO. Oct. 11, 1962 [Feb. 8, 1962], No. 38585/62. Headings B3A, B3E and B3R. In welding opposed edges of a pair of metal portions of finite length, the portions are advanced with the edges spaced, flows of highfrequency current are maintained over the edges in advance of a weld point and re-usable extension circuit means are provided electrically in series with the edges to form a conductive path for current to interconnect the edges as they approach the weld point the circuit means, which do not become welded together or to the portions being separated from the portions. A steel tube 20, Fig. 2 (not shown), is provided with force-fitted copper split ring end members 22, 24 and while being advanced between rollers 27, 28 is supplied with current of frequency of 50-400 kc. per sec. by contacts 31, 32. The copper split rings provide current paths but do not become welded and are removed after the tube 20 is welded. The current may be applied inductively. The ring end members need not close completely when a roller is used to complete the circuit across the edge of the forward member. In another embodiment flat steel metal elements 42, Fig. 5 (not shown), are placed on a phosphor bronze, copper or stainless steel endless belt 40 and as the belt advances rollers including rollers 46, 50, 51, 52, 53 curl the belt into gapped cylindrical form 44 and form the workpieces to gapped tubular form adjacent the welding station. The belt straightens out once past the station and at a point subsequent to the station a roller 63 is provided to electrically interconnect the belt edges. The rollers 52, 53 bring the workpiece edges to butted or overlapped relation and an upper roller 59 and a co-operating lower roller engage the workpiece at the weld point. In advance of the weld point an induction coil 64 supplied with current of at least 10 kc. per sec. surrounds the belt and workpieces and induces current to flow in the edges of the workpieces and in the edges of the belt across the roller 63. The workpiece edges are thus heated before they contact at the weld point. An internal induction coil or contacts engaging the edges of the workpieces may be employed instead. In another embodiment gapped cylindrical workpieces are each inserted in a cylindrical carrier 72, Fig. 10 (not shown), having a wider gap 73, the carriers are advanced on a chain 75 and at the weld point an annular group of pressure rollers embrace the carriers to bring together the edges of the workpieces heated by current induced by an internal coil 78 and following a path in the carrier completed by a roller 82. Rolls 85, 86 effect a mash lapped seam. In a modification a carrier is arranged within the workpieces. In another embodiment gapped workpieces 100, Fig. 17 (not shown), encircle a stationary structure 102 carrying high-frequency supplied contacts 103, 104 extending under the edges of the workpieces and connected beyond the weld point w by a bridge 105. Rollers 110 advance the workpiece and rollers 111, 112 close the edges at the weld point. Above the edges insulating members press the edges into contact with the members 103, 104. Strip members may be welded by the method of the invention.